Mesozoic Two-phase Folds And Its Implications In Dabaoshan Plymetallic Ore Deposit,North Guangdong Province

The Dabaoshan Cu-Pb-Zn-Mo-W-Fe polymetallic deposit is located at the middle part of the Nanling granite belt,South China,Which is a famous large deposit with a long history of mining.This deposit has the characteristics of many types of deposits,diverse metallogenic elements,complex formation and so on,which has been widely concerned by many geological workers since the mining.Studies of the deposit have focused on diagenetic geochronology,deposit characteristics,mineralizing models and mechanism.However there are still some key issues unresolved,such as the mine structural features,it is affect the overall understanding of the deposit.In this paper,we chose the deposit as the research object,based on the field geological investigation and referring to previous work,the field data collection and indoor analysis,combined with previous theories,we analysis and discussion on the deformation characteristics of the structure of the deposit.Therefore,this paper chose “Mesozoic Two-phase folds and its implications in Dabaoshan Plymetallic Ore Deposit,North Guangdong Province” as the title to correct and supple the previous research.At the same time,make a good comprehension about the tectonic characteristics,geological features and tectonic evolution of the area.Through the above work we can provide some important reference value advice for the later of scientific research and production.The major conclusions are summarized below:(1)Two phase fold deformation developed in the Dabaoshan Mine at Mesozoic,which records distinctly its history of the structure deformation and is beneficial to research on tectonic evolution.Through the system research on folds,quartz vein,cleavage,knee fold of the Dabaoshan deposit,we identified two generations of superimposed folds that the earlier generation of folds is obvious,roughly NNW trending,and the later one is not obvious,nearly E-W trending.(2)Through the analysis of the deformation characteristics of outcrop superimposed folds and combined with regional fold tectonic line,we proposed the earlier generation of superimposed folds in Southern China should be nearly north-south,the later generation of superimposed folds in Southern China should be nearly east-west.Based on the analysis of the intersection relationship of multi period tectonic deformation in Dabaoshan mine,quartz molybdenite age data and regional geological events,we think the N-S trending folds were generated as the far-field effect of a low angle subduction of the Paleo-Pacific oceanic plate beneath the South China Block,which occurred in Early-Late Jurassis(175-165Ma).In the late stage(after 175-165Ma)there are existed nearly N-S compression formed nearly East-West folds.(3)On the basis of the relationship between the structure and mineralization in Dabaoshan mine,the tectonic evolution history from early to late was established,which include Early-Late Jurassic(208-161Ma)E-W compression that formed nearly N-S trending folds,the planar distribution of silicon or quartz-pyritization,the later(after 165Ma)nearly N-S compression that formed nearly E-W trending folds.Early folding formed Dabaoshan syncline that constitute the basic tectonic framework of the Dabaoshan mine,which provides a favorable channel and storage space for the late magmatic mineralization.After magmatism in Yanshan period is the main metallogenic stage,the pyritization planar distribution of silicification and quartz development within the mining area,in some place mineralized alteration distribution in hinge zone of the early fold.Late folding transformation and superposition of the early folds,and outcrop superimposed folds can found in some place.